Hydrocarbon oil extraction



Patented May 9, 1939 orrrc.

ROCARBON OIL EXTRACTION N Drawing.

Application July 3, 1933,

Serial No. 678,928 I Claims.

The present invention relates to the art' of mineral oil refining and has particular reference to the improvement of lubricating oils, and more particularly and specifically to the removal of 5 color bodies and/or asphaltic materials from petroleum oils substantially simultaneously with removal therefrom of naphthenic bodies.

In accordance with my invention, crude pe' troleum or petroleum fractions, particularly viscous petroleum oils, and more particularly residuums having an initial boiling point of more than 412 F., are simultaneously subjected to treatment with a selective solvent and a low boiling hydrocarbon or mixture of low boiling hydrocarbons to eiiect a separation of the oil fractions, and to produce a paraflinic fraction of enhanced value from the standpoint of color.

It is recognized in the art that mineral oils, such as petroleum, comprise essentially a mixture of hydrocarbons of'various groups or homologous series of compounds, such as paraffins, olefines, hydroaromatics and polymethylenes, and other series of compounds of chain and/or ring structure. The various types of crude petroleum, which are generally classified into three groups, namely, paraffin base, naphthenic or asphaltic base, and mixed base, contain the various series of hydrocarbons mentioned heretofore in difierent proportions.

These hydrocarbon groups comprising the different types of crude petroleum possess a differential solubility in selective solvents, the naphthenic and/or asphaltic compounds exhibiting, in general, a much greater solubility in said solvents than the parafiinic.

I find that in the extraction of highly viscous oils, and particularly residuums, it is of considerable advantage to carry on the extraction process in the presence of low boiling hydrocarbons, such as petroleum naphtha, or other low molecular weight parafiin hydrocarbons. The marked reduction in viscosity of the oil undergoing treatment, and the increase in the specific gravity difierential between the solvent and oil is an important factor in the eflicien-t separation of the undissolved oil and solvent layers. It will be readily understood that in the extraction of viscous oils, and particularly waxcontaining oils or residuums, the presence of low boiling paraffin hydrocarbons which are relatively immiscible with the selective solvent, will effect reduction of the viscosity of the undissolved oil layer, increase the gravity differential between said layer and solvent, and increase the volume of the undissolved oil layer in which the bulk of the wax is concentrated, thereby to decrease the entrainment of solvent and greatly improve the rapidity and completeness of separation of the layers.

I have found that in the selective solvent extraction ofpetroleum oils, the color imparting or asphaltic bodies are concentrated, to a great extent, in the fraction of the oil which dissolves in the solvent, 1. e., the naphthenic portion of the oil. Petroleum oils, particularly residuums or oils derived'from same, contain asphaltic or color imparting bodies which are suspended or dispersed in the oil as finely divided solid particles, the said dispersion being stabilized by a peptizing agent such as resinous compounds commonly occurring in mineral oils. In the selective solvent extraction process, using, for example, nitrobenzene as a solvent, both the asphaltic or color bodies and the peptizing agent are soluble in the nitrobenzene, and while they are to a large extent concentrated in the nitrobenzene soluble oil layer, the undissolved oil layer contains suflicient nitrobenzene as to render a small quantity of the color imparting or asphaltic bodies, as well as the resinous material soluble in said undissolved layer.

However, I have found that if the solvent extraction be' carried on in the presence of low boiling petroleum naphtha or low molecular weight paraflin hydrocarbons, the color of the undissolved oil fraction will show a substantial improvement over that obtained byextraction with a selective solvent alone. In as much as the asphaltic and/or color-imparting bodies are relatively insoluble in the low molecular weight :1) paraffinic diluents, which in turn, are relatively immiscible with the selective solvent,-the addition of such hydrocarbons to the oil being extracted will thereby decrease the solubility of said asphaltic bodies in the undissolved oil layer 1 and tend to further concentrate said bodies in the solvent layer.

My invention, therefore, comprises a process whereby an improvement in color and in other properties of a viscous mineral oil is obtained by bringing the oil stock into contact .with a selective solvent in the presence of a suitable quantity of'low molecular weight paraflinic hydrocarbons, thereby effecting solution of a portion of the oil in said solvent, allowing the mixture to settle, separating the diluent layer containing the paraflinic oil from. the solvent layer containing the major portion of the naphthenic oil and asphaltic bodies and removing the solvent and diluent from both layers as by distillation. The undissolved oil fraction may be repeatedly extracted or the entire extraction may be carried'on in a continuous countercurrent system, and under conditions of incomplete miscibility.

My process may be illustrated by the following examples:

An Ecuadorian crude oil was reduced by distillation to a 13.2% residuum having a viscosity of 236 seconds Saybolt Universal at 210 F., and an A. P. I. gravity of 174 at 60 F. 1 volume of the said residuum was mixed with 1 volume of extraction naphtha and 1 volume of nitrobenzene and the mixture heated to slightly above the temperature of complete miscibility. Upon cooling the mixture to 10 C., and allowing the mixture to settle, a two layer system was formed. After separation of the layers by decantation and removal of the nitrobenzene and diluent from each, by vacuum distillation, the undissolved oil fraction comprising 60% of the stock was diluted with extraction naphtha in the ratio of 30 parts of oil to '70 parts of naphtha. The resulting solution was then filtered thru clay and a yield of bb1s/17 tons of clay was obtained, having a N. P. A. color of from 4 to 4%,. Upon extracting 1 volume of the same Ecuadorian residuum with 1 volume of nitrobenzene, in the above described manner, but in the absence of any hydrocarbon diluent, there was obtained an undissolved oil fraction comprising 70% of the stock. This fraction was diluted in the 30/70 ratio, as above, with naphtha, and clay filtered, whereby a yield of 149 bb1s/17 tons of clay was obtained, having a color darker than 8 N. P. A.

As a further illustration, 1 volume of the above mentioned residuum was extracted with 1 volume of nitrobenzene, in the presence of volume of extraction naphtha. The same procedure as used in the above examples gave an undissolved oil fraction comprising 65% of the stock, which upon dilution with 30/70 ratio of naphtha, and clay filtration, gave a yield of 142 bbls/ 17 tons of clay, having a N. P. A. color of 3 When 1 volume of the Ecuadorian residuum was extracted with 1 volume of nitrobenzene, in the absence of any hydrocarbon diluent, in accordance with the above procedure, there resulted an undissolved oil fraction comprising 73% of the stock, which upon dilution with naphtha and clay filtration, yielded 112 bbls/17 tons of clay, having a N. P. A. color of from 4 to 4%.

Further examples illustrative of the results obtained by operating in accordance with my process are summarized in the following table:

a substantial improvement in color, as compared with solvent extraction in the absence of low boiling hydrocarbon diluent. Moreover, the mechanical difilculties involved in the extraction of viscous or waxy oils are, to a great extent, overcome in my process by the advantages hereinbefore described.

Herein, while I have discussed the theories which I believe underlie my invention, it is to be understood that I do not intend to be held thereto, as my invention is in no way predicated upon the correctness of the theories herein set forth.

My process, while designed primarily for the treatment of heavy residuums, is also applicable to materials such as viscous distillates contaminated with residuums, as for example, as a result of entrainment during the distillation process, as well as other oils which contain asphaltic or color bodies adapted to removal by an extraction process.

Herein, and in the appended claims, the term "viscous oil is to be understood to refer to oils of substantial viscosity, that is, of the order of 50 seconds or more Saybolt Universal viscosity at 100 F. The term low boiling hydrocarbon diluent" comprehends low boiling petroleum naphthas, propane, butane, pentane and other low molecular weight paraffin hydrocarbons or mixtures of low molecular weight hydrocarbons in which paraflinic hydrocarbons predominate. The term selective solvent is to be understood to comprehend any one or more of the solvents mentioned by Ferris, Girkhimer, and Henderson in their article in Industrial and Engineering Chemistry, vol 23, page 753 (1931) and more particularly and specifically organic selective solvents, as for example, nitrobenzene, aniline, pyridine, acetone and such like, or selective solvents which under normal or atmospheric conditions of temperature and pressure are liquid.

What I claim is:

1. In the art of refining mineral oils, the proc ess which comprises bringing a viscous hydrocarbon oil containing naphthenic and paraflinic hydrocarbons and asphaltic or color-imparting bodies into contact with a. mixture of nitrobenzene and low boiling hydrocarbon diluent, thereby to divide the oil into at least two fractions, one of which is poorer in naphthenic hydrocarbons and asphaltic or color-imparting bodies, separating said fractions, and removing the nitrobenzene and diluent from at least one of the fractions so separated.

2. In the art of refining mineral oils, the process which comprises mixing a viscous oil con- Ylald un- Sa Univ. A. P. I. O. D Holde stock dis. oil fla /210 F. gravity color asphalt Percent Second: Degrees Barber's hill residuum. 401 16. 8 0. 871 32, 600 0. 85

Solvent treatment Undissolved oil fraction 2 volumes of aniline er volume of stock 63. 0 352 18. 8 0. 855 34, 200 0. 30 2 volumes of aniline 4 volumes of ext. naphtha per volume of stock 87. 5 379 17. 4 0. 868 33. 550 0. 36

2 volumes of nitrobcnzene per volume oi stock- 65. 0 226 21. 7 0. 838 17. 900 2 volumes of nitrobenz ne+4 volumes of propane per volume of stock 61. 3 187 23. i 0. 831 3, 280 2 volumes of nitrobenzene+8 volumes of propane per volume of stork 64. 0 22. 0 0. 835 2. 260

From the foregoing examples, it will be seen that by my process of extraction with a selective olvent in the presence of a suitable quantity of low boiling hydrocarbon diluent, there is obtained taining naphthenic and paraifinic hydrocarbons and asphaltic or color-imparting bodies with nitrobenzene and a low boiling hydrocarbon dil uent, heating the mixture to a temperature sufilaitmai cient to efi'ect solution, cooling the solution to cause a separation into layers, removing the upper layer, andremoving nitrobenzene and diluent from said layer.

3. In a process forseparating mineral oil con-- taining paramnic and naphthenic constituents into fractions respectively more paramnic and more naphthenic than the original oil, the step comprising extracting the oil, in the presence of a liquid having greater solvent power for paraffinic constituents than for naphthenic constituents, with nitrobenzene the said paramnic solvent and nitrobenzene being adapted to form atwolayer liquid system in contact with each other.

1. In a process for separating mineral oils containing paramnic and naphthenic constituents into fractions respectively more paraflinic and more naphthenic than the original oil, the step comprising extracting the oil in the presence of a low boiling hydrocarbon diluent with 9. nitrogen-containing cyclic compound, the said diluent and nitrogen-containing cyclic compound being adapted to form a two-layer liquid system in contact with each other.

5. In a process for separating mineral oils containing parafiinic and naphthenic constituents into fractions respectively more pare and more naphthenic than the original oil, the step comprising extracting the oil in the presence of a low boiling hydrocarbon diluent with a nitrogenecontaining carbocyclic compound, the said diluent and nitrogen-containing carbocyclic compound being adapted to form a two-layer liquid system in contact with each other. 

